1. Field of the Invention
The present invention relates to a process for the preparation of ceramide utilized as a skin moisture-keeping component, and provides a process for acquiring ceramide cheaply and in bulk, which has been hithertofore unknown.
2. Prior Art
It is known that nerve tissue of mammal contains sphingolipid which is a ceramide derivative. The sphingolipid of bovine brain is utilized as it is, without conversion to ceramide, as a crude material for cosmetics. (cf. Official Gazette of Patent Kokai Sho 64-16708. Supplement to the Japanese Cosmetic Ingredients Codex 1993 "523019 Bovine Brain Extract"and "523017 Bovine Brain Lipid").
On the other hand, the following references report a process for decomposing sphingolipid to obtain ceramide:
Hydrolysis by using hydrogen fluoride (cf. Reddy, P. V.; Natarajan, V; Sastry, P. S.: Chem. Phys. Lipids, 1976, 17, 373-7).
Enzyme-decomposition by means of phospholipase produced by bacteria.
However, there has not been reported any process for preparation of ceramide by applying these methods.
No process has ever been established, in which ceramide is cheaply acquired from sphingolipid by using erythrocytes of cattle and poultry as starting materials.
Human rough skin occurs when moisture has been lost due to dermatitis and the like or under a physiological requirement and dry environments, etc. Rough skin is of course not only an aesthetic problem but also dermatologically undesirable because of a decrease in the protective action which the skin has.
For curing such a rough skin, medicines for external use such as ointments, lotions, etc. and cosmetics such as creams, milky lotions, etc. may be used. These pharmaceutical preparations or cosmetic formulations functionally keep skin in a healthy state at around 20% moisture thereof. For this purpose are used emulsifiable base agents having a function resembling a sebum cutaneum membrane existing on the skin, and lactic acid existing in the skin, and components of so-called natural moisturing factors (NMF) such as pyrrolidone carboxylate, amino acids, etc.
Recently, it has been found that the stratum corneum intercellular lipid, which is mainly composed of ceramide, promotes retention of skin moisture. Addition of a sufficient amount of ceramide can strengthen the effect of a preparation for rough skin. Accordingly, it has been desired to cheaply supply large quantities of ceramide.
Sphingolipids (ceramide derivatives such as sphingomyelin, glucosylceramide, etc.) used as a raw material have until now been said not to exist in the stratum corneum intercellular lipid. Such substances contain large highly polar substituents such as phosphorylcholine, saccharide, etc. which are much different in property from ceramide. In order to supplement the inherent water-retention function which the skin has, the present inventors have aimed at the application of ceramide per se and devoted themselves to studying the processes of preparing ceramide. As a result, they have developed a process wherein sphingolipid is efficiently extracted from living materials, which is further followed by conversion to ceramide.
For such purpose, various sources of readily available raw material for obtaining ceramide have firstly been pursued.
Heretofore, raw materials for sphingolipid were sought from nerve tissues such as bovine brain and the like, as mentioned above in Japanese Patent Kokai Sho 64-16708 and its cited literatures, and also in the Supplement to the Japanese Cosmetic Ingredients Codex 1993 "Bovine Brain Extract", "Bovine Brain Lipid", etc. However, such a source is expensive because of the limited amounts available, and therefore, sufficient necessary amounts are supplied only with difficultly. From such a viewpoint, the present inventors have paid attention to erythrocyte as source of ceramide.
Cattle and poultry are bred on a large scale for food. Accordingly it is well known fact that a large amount of blood is released every time they are butchered. For use in tissue culture and the like, blood serum and plasma protein are produced from blood in large quantities. In addition, from hemocytes which were left after obtaining blood serum, hemoglobin is extracted to be utilized as medicines and foods. On the other hand, the finally remaining erythrocyte membrane after the production of blood serum and hemoglobin from blood is now of no use and therefore, such a membrane will be discarded with much expense at the present stage.